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- ItemWater Splitting on Multifaceted SrTiO3 Nanocrystals: Calculations of Raman Vibrational Spectrum(MDPI, 2022) Krasnenko, Vera; Rusevich, Leonid L.; Platonenko, Aleksander; Mastrikov, Yuri A.; Sokolov, Maksim; Kotomin, Eugene A.Various photocatalysts are being currently studied with the aim of increasing the photocatalytic efficiency of water splitting for production of hydrogen as a fuel and oxygen as a medical gas. A noticeable increase of hydrogen production was found recently experimentally on the anisotropic faces (facets) of strontium titanate (SrTiO3, STO) nanoparticles. In order to identify optimal sites for water splitting, the first principles calculations of the Raman vibrational spectrum of the bulk and stepped (facet) surface of a thin STO film with adsorbed water derivatives were performed. According to our calculations, the Raman spectrum of a stepped STO surface differs from the bulk spectrum, which agrees with the experimental data. The characteristic vibrational frequencies for the chemisorption of water derivatives on the surface were identified. Moreover, it is also possible to distinguish between differently adsorbed hydrogen atoms of a split water molecule. Our approach helps to select the most efficient (size and shape) perovskite nanoparticles for efficient hydrogen/oxygen photocatalytic production. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
- ItemTriboelectric behaviour of selected MOFs in contact with metals(Royal Society of Chemistry, 2022) Šutka, Andris; Shieh, Fa-Kuen; Kinka, Martynas; Lapčinskis, Linards; Chang, Chien-Chun; Lam, Phuc Khanh; Pudzs, Kaspars; Verners, OsvaldsMOFs have been effectively used to magnify the triboelectric charge of polymers. However, so far the individual triboelectric properties and charge transfer mechanisms of MOFs haven't been reported. Triboelectric property investigation for selected MOFs show that the main mechanism for MOF triboelectrification in contact with metals is electron transfer. © 2023 The Royal Society of Chemistry.--//-- This is an open access article Šutka A., Shieh F.-K., Kinka M., Lapčinskis L., Chang C.-C., Lam P.K., Pudzs K., Verners O., "Triboelectric behaviour of selected MOFs in contact with metals" (2022) RSC Advances, 13 (1), pp. 41 - 46, DOI: 10.1039/d2ra06150c published under the CC BY and CC BY-NC licence.
- ItemTribological and Mechanical Properties of the Nanostructured Superlattice Coatings with Respect to Surface Texture(MDPI, 2022) Jansons, Ernests; Lungevics, Janis; Kanders, Uldis; Leitans, Armands; Civcisa, Guna; Linins, Oskars; Kundzins, Karlis; Boiko, IrinaCeramic Nanostructured Superlattice Coatings (NSC) have broad applicability to improve the parts’ and assemblies’ tribological and mechanical properties for the needs of the automotive and aerospace industries. Improving the material properties using nanocoatings for such a widely used material as, for example, bearing steel 100Cr6 makes it possible to improve the service life of machine parts. In this paper, the correlation dependence between tribological and mechanical properties of the NSC and its surface texture are considered to determine how much surface texture will affect the tribological performance of the coated workpieces, as well as the measuring and evaluation procedure of the nanocoatings, are presented. Three different NSC described by a general empirical formula {TiMe1Me2-CN/TiAlSi-N}n and based on the modified carbonitride/nitride non-stoichiometric chemical composition were created, and their tribological and mechanical properties measured and analyzed in the context with surface texture. NSC deposited by the advanced PVD (Physical vapor deposition) technique demonstrated significantly higher wear resistance (up to 28 times), reasonably lower friction coefficient (CoF) (up to 4 times), and significantly higher hardness of the coated workpieces (up to 7 times) versus substrate material. A strong correlation between the steady-state dry sliding friction, CoF, and the amplitude and functional surface texture parameters of tribo-track were observed. The first results of the initiated research regarding the correlation analysis of the tribological and mechanical properties, on the one hand, and surface texture, on the other hand, of the NSC are reported here. © 2022 by the authors.
- ItemTheoretical Development of Polymer-Based Integrated Lossy-Mode Resonance Sensor for Photonic Integrated Circuits(MDPI, 2022) Letko, Edvins; Bundulis, Arturs; Mozolevskis, GatisA promising phenomenon such as lossy-mode resonance (LMR) is of great interest in sensor applications. Until now, this phenomenon has been shown only in fibers or planar waveguides; however, given the rapid development of such an important technological area as photonic integrated circuits (PICs), it is important to transfer LMR technology specifically to PICs. In this article, we propose the theoretical development of an integrated polymer-based LMR sensor that will also contribute to the development of hybrid organic–inorganic PICs. This work theoretically shows that LMR can be achieved using polymer SU-8 waveguides on a glass substrate, on top of which TiO2 is deposited. In addition, the paper shows that multiple resonances can be achieved in the developed integrated sensor. The highest sensor sensitivity (about 1400 nm/RIU) was achieved with 40 nm of TiO2. The effect of the waveguide and coating geometries, as well as the polarizations of propagating modes, is studied in this paper. © 2022 by the authors.
- ItemSelective Disintegration–Milling to Obtain Metal-Rich Particle Fractions from E-Waste(MDPI, 2022) Blumbergs, Ervins; Serga, Vera; Shishkin, Andrei; Goljandin, Dmitri; Shishko, Andrej; Zemcenkovs, Vjaceslavs; Markus, Karlis; Baronins, Janis; Pankratov, VladimirVarious metals and semiconductors containing printed circuit boards (PCBs) are abundant in any electronic device equipped with controlling and computing features. These devices inevitably constitute e-waste after the end of service life. The typical construction of PCBs includes mechanically and chemically resistive materials, which significantly reduce the reaction rate or even avoid accessing chemical reagents (dissolvents) to target metals. Additionally, the presence of relatively reactive polymers and compounds from PCBs requires high energy consumption and reactive supply due to the formation of undesirable and sometimes environmentally hazardous reaction products. Preliminarily milling PCBs into powder is a promising method for increasing the reaction rate and avoiding liquid and gaseous emissions. Unfortunately, current state-of-the-art milling methods also lead to the presence of significantly more reactive polymers still adhered to milled target metal particles. This paper aims to find a novel and double-step disintegration–milling approach that can provide the formation of metal-rich particle size fractions. The morphology, particle fraction sizes, bulk density, and metal content in produced particles were measured and compared. Research results show the highest bulk density (up to 6.8 g·cm−3) and total metal content (up to 95.2 wt.%) in finest sieved fractions after the one-step milling of PCBs. Therefore, about half of the tested metallic element concentrations are higher in the one-step milled specimen and with lower adhered plastics concentrations than in double-step milled samples. © 2022 by the authors.--//-- This is an open access article Blumbergs E., Serga V., Shishkin A., Goljandin D., Shishko A., Zemcenkovs V., Markus K., Baronins J., Pankratov V. "Selective Disintegration–Milling to Obtain Metal-Rich Particle Fractions from E-Waste" (2022) Metals, 12 (9), art. no. 1468, DOI: 10.3390/met12091468 published under the CC BY 4.0 licence.